In Xcode, press the compile button to build and then run the current
scheme. The build produces an error, prompting you to enter your API key
in the SDKDemoAPIKey.h file.

If you don't yet have an API key, follow the
instructions to set up
a project on the Google Cloud Platform Console and get an API key. When configuring the
key on the Google Cloud Platform Console, you can specify your app's bundle identifier to
ensure that only your app can use the key. The default bundle identifier of
the SDK samples app is com.example.GoogleMapsDemos.

Edit the SDKDemoAPIKey.h file and paste your API key
into the definition of the kAPIKey constant. For example:

static NSString *const kAPIKey = @"YOUR_API_KEY";

If Xcode prompts you to unlock the SDKDemoAPIKey.h file for
editing, choose Unlock.

Remove the following line, because it's used to register the user-defined
issue:

#error Register for API Key and insert here.

Build and run the project. The iOS simulator window appears, showing
a list of Maps SDK Demos.

Choose one of the options displayed, to experiment with a feature of the
Maps SDK for iOS.